This invention relates to a novel solid catalyst component to be employed with a cocatalyst for use in the polymerization of olefins to polyolefins such as polyethylene, polypropylene and the like, or copolymers such as ethylene copolymers with other alpha-olefins and diolefins, which catalyst component shows unusually high activity, excellent hydrogen response for the contol of polymer molecular weight and good comonomer response for the production of copolymers. The polymer product obtained has a good balance of polymer properties, for example, the catalyst system obtains a polymer with a broad molecular weight distribution and an improved balance in polymer product machine direction tear strength and transverse direction tear strength. As a result, the blown film produced from the polymer product manifests an overall higher strength.
The catalyst component comprises a solid reaction product obtained by contacting a solid, particulate, porous support material such as, for example, silica, alumina, magnesia or mixtures thereof, for example, silica-alumina, with an organoaluminum compound, a vanadium compound and a halogenating agent. The novel catalyst component, which when used with an aluminum alkyl cocatalyst, provides the novel catalyst system of this invention which can be usefully employed for the polymerization of olefins.
The catalyst system can be employed in slurry, single-phase melt, solution and gas-phase polymerization processes and is particularly effective for the production of linear polyethylenes such as high-density polyethylene and linear low denisty polyethylene (LLDPE).
It is known that catalysts of the type generally described as Ziegler-type catalysts are useful for the polymerization of olefins under moderate conditions of temperature and pressure. It is also well known that the properties of polymer product obtained by polymerizing olefins in the presence of Ziegler-type catalysts vary greatly as a function of the monomers of choice, catalyst components, catalyst modifiers and a variety of other conditions which affect the catalytic polymerization process.
For the production of high strength film, it is desirable that polymer product have a high molecular weight. However, high molecular weight resins such as polyethylene, which generally are of a narrow molecular weight distribution are difficult to process.
It is therefore desirable to provide polyolefin resins having a high molecular weight so as to obtain high strength films therefrom coupled with a broad molecular weight distribution so as to provide an easily processable resin. It is furthermore highly desirable that the resin be produced by a commercially feasible and economical process which obtains polymer product having a good balance of properties.
U.S. Pat. No. 4,434,242 of Roling et al, issued Feb. 28, 1984, teaches a polymerization process for preparing injection molded resins by polymerizing ethylene in the presence of a vanadium based catalyst. However, as taught in the patent, the process provides resins having a narrow molecular weight distribution suitable for injection molded resins rather than blown molded resins.
In European Patent Application 55589, Asahi teaches treating an oxide support with an organomagnesium composition, a chlorosilane and then treating with a titanium or vanadium compound that has at least one halogenated atom. As demonstrated in Example 7, the resin obtains a relatively narrow molecular weight distribution which is statistically in the same range as the resins produced in the presence of titanium based catalysts.
British No. 2,105,355 describes a gas-phase method for making elastomeric copolymers of ethylene and higher alpha-olefins in the presence of a vanadium-based catalyst. The catalyst is prepared by sequentially treating an inert oxide support with a vanadium compound, and an aluminum alkyl compound. The catalyst is not taught to be useful for the production of injection molded or blow molded resins but rather produces an elastomeric product.
Soviet 422,192 treats a silica support with an organoaluminum compound and a chlorinating agent and thereafter adds TiCl.sub.4 to the material so as to obtain an active catalyst. The production of polyetylene having a high molecular weight and coupled with a broad molecular weight distribution is not disclosed.
In U.S. Pat. No. 4,435,518 of Pennington a process is disclosed for the production of resins having a narrow molecular weight distribution by polymerizing an olefin in the presence of a catalyst composition comprising an inorganic oxide support treated with an organometallic compound such as trialkylaluminum, further treated with vanadium compound and finally treated with an alcohol.
In U.S. Pat. No. 4,435,519 of Veazey also teaches the production of polyolefins such as polyethylene having a narrow molecular weight distribution in the presence of a vanadium-based catalyst, said catalyst obtained by treating an inorganic oxide support with an organometallic compound such as triethylaluminum, and a vanadium compound.
The above patents do not suggest how its processes might be modified to result in the formation of polymers having a broad molecular weight distribution coupled with a high molecular weight so as to provide resins suitable for the production of high-strength films.
Furthermore, the patents do not disclose catalyst systems which show excellent responsiveness to hydrogen during the polymerization reaction for the control of molecular weight, do not disclose or evidence the excellent comonomer response so as to produce ethylene copolymers and particularly LLDPE, and particularly do not disclose highly active catalyst systems which all produce a high molecular weight-broad molecular weight distributed polymeric resin.
In my cofiled appliction, U.S. Ser. No. 680,871filed Dec. 12, 1984, I disclose a catalyst system comprising a vanadium containing solid obtained by treating an inert support material with an organoaluminum compound, an acid halide and a vanadium compound.
In accordance with this invention catalyst combinations have been found which have extremely high catalytic activites, good comonomer incorporation, excellent hydrogen responsiveness for the control of molecular weight and obtain polymer product manifesting a broad molecular weight distribution with greatly improved film properties. The resins exhibit excellent melt strength with a surprising decrease in power consumption, hence an increase in extrusion rates.
The new catalyst systems and catalyst components of this invention ae obtained by contacting an organoaluminum compound, a halogenating agent and a vanadium metal compound n the presence of an oxide support. The catalyst system employing the vanadium based catalyst component is advantageously employed in a gas phase ethylene polymerization process since there is a significant decrease in reactor fouling as generally compared with prior art ethylene gas phase polymerization processes thereby resulting in less frequent reactor shut downs for cleaning.